ITPD20060348A1 - MOBILE SYSTEM FOR THE ACQUISITION OF NEURONAL ACTION POTENTIALS AND THEIR REAL-TIME TELEMETRIC TRANSMISSION WITHOUT WIRES. - Google Patents

Description

PD 2 0 U b A U U U O 't O

7462PTIT Notarbartolo & Gervasi S.p.A.

Description of the industrial invention entitled:

“MOBILE SYSTEM FOR THE ACQUISITION OF POTENTIALS OF

NEURONAL ACTION AND THEIR REAL-TIME TELEMETRIC TRANSMISSION VIA DIGITAL WIRELESS "

on behalf of: SISSA - International School of Advanced Studies

Advanced

based in: Trieste

designated inventors: DIAMOND, Mathew E .; PERKON Igor; ZORZIN, Erik

FIELD OF THE INVENTION

The invention relates to an integrated system for capturing,

amplification, analog conditioning, analog-to-digital conversion, digital processing, wireless transmission and reception

real-time digital neuronal electrical signals, visualization

digital recording of such signals, the digital recording of the signals into a computer

and to the method of acquisition and processing of such signals with the

same.

STATE OF THE TECHNIQUE

The measurement of neuronal activity plays a fundamental role in

scientific research both in the laboratory and in the clinic. In the case of the

laboratory, the study of neuronal activity in experimental animals

allows us to investigate the functioning mechanisms of the brain. In

clinical, the same approaches offer the possibility to understand the basics

neuronal diseases of neurological affections and to develop therapies

innovative to treat them.

7462PTIT Notarbartolo & Gervasi S.p.A.

neuronal diseases of neurological diseases and to develop innovative therapies to treat them.

Different types of electrical signals characterize the neuronal activity of an animal or human subject.

If on the physiological side it is essential to know the complex relationships in the neuronal response to stimuli of various kinds, even more essential is the study of neuronal activity in pathological conditions, such as in epilepsy. It is in fact known that brain activity is subject to fine regulation due to the reciprocal relationships between different neuronal systems and that many neurological pathologies are characterized by dys-regulation of the neuronal activity of specific systems.

A particular type of neuronal electrical signals of interest for this type of study are those electrical impulses generated by neurons that are characterized by a stereotypical waveform electrical voltage fluctuation called an "action potential". In fact, the action potential is the elementary electrical signal that is generated by neurons and these potentials are generally of the order of pV (for example, between 100

and 500 pV) and have a duration of milliseconds (for example 1-1.5msec).

Neurons are interconnected by multiple connections that make up the physical channels through which electrical signals are exchanged. Electrical signals can be characterized by their time sequences and spatial distributions of action potentials. The sequences and distributions constitute the words of a language composed of messages that correspond to the encoding of complex functions or behaviors such as, for example, sensations, perceptions, movements and decisions.

7462PTIT Notarbartolo & Gervasi S.p.A.

The measurement of action potentials integrates with the study of neuronal language as it provides data for mathematical models of the functioning of the brain, or parts of it. In these models, neurons are represented by nodes of information exchange that travels through a network of interconnections, called the "neural network".

The study of the neuro-electrical signals, understood as action potentials, of individual neurons is therefore essential for understanding the mechanisms of regulation of nerve responses both in physiological and pathological conditions.

The standard survey involves the use in the laboratory of animals, very often small rodents, which for scientific or legal / legal methodological reasons are suitable to be the subjects in the experiments.

The traditional system for measuring neuronal activity is based on the use of electrodes inserted in the brain of the subject and connected via an electric cable to recording systems controlled by a computer.

Different types of experiments can be conducted and in general two broad categories can be considered: "acute" and "chronic".

During acute experiments the subject is under the effect of anesthesia

general, therefore immobile and devoid of conscience. However, many of the cerebral and subcerebral areas remain active and their study is still possible. The restriction to the study of these areas in these conditions is useful in relation to the fact that making neuronal recordings from an immobile subject simplifies the experiment from a technical and operational point of view.

7462PTIT Notarbartolo & Gervasi S.p.A.

Chronic experiments, on the other hand, are characterized by an awake and physically active subject. This last case is interesting because only in this condition it is possible to study the relationships between the behavior of the subject under examination and the neuronal signals present in his brain, which are supposed to govern his behavior.

The "subject-cable-equipment" configuration adopted so far by traditional systems also in chronic experiments derives substantially from the need to have an electric cable for connecting equipment which, due to their size, cannot be installed directly on the subject. This feature inherently leads to several categories of problems.

The first and most obvious limitation of a cable measuring system is the limitation due to the weight of the detection system itself. In fact, the subject is subjected to the weight of the detection system and the cable necessary for the transmission of the electrical signal from the subject to the acquisition and analysis apparatus of the same. In small animals, such as small rodents, the weight and dimensions of the equipment necessary for measuring neuronal signals can be strongly constraining, if compared to the weight and therefore to the

muscle strength of the subject. Different forces limit the movement of the subject and the perception of himself in the environment. These factors can alter the subject's behavior to an extent that they distort behavioral studies in chronic experiments.

A second limit always deriving from the presence of the connection cable between the subject and the acquisition and analysis apparatus of the

7462PTIT Notarbartolo & Gervasi S.p.A.

electrical signal, is of course the spatial limitation to which the subject

is subjected, being that some movements of the subject are inhibited or

strongly hindered by the presence of the cable. The typical case is when the

subject must move around obstacles (an example can be

also the passage through a tunnel that can be part of experiments

on methods of navigation and path recognition): movement

three-dimensional is prevented and therefore an entire branch of

behavioral experiments is severely impaired.

A third and significant limitation is the related electrical problem

to the acquisition and analysis of a relatively weak electrical signal e

of short duration, such as the neuronal action potential. Because of

physical distance between the subject and the equipment and theirs

interconnections, power lines often introduce differences of

electric potential difficult to control that disturb the

registrations. These phenomena are known as ground loops e

in the worst case they can cause damage to the person himself or to

equipment.

A fourth problem, related to the previous one, is that of electrical noise

introduced by the power supply network, usually around

50/60 Hz. This leads to two important negative consequences. There

first consists in the fact that the high amplitude of these signals can

induce saturation of the signal amplification stages and therefore

favor their damage. The second, on the other hand, is natural

purely technological. It happens that the saturation of the stage of

amplification operates a non-linear transformation of the signal from

7462PTIT Notarbartolo & Gervasi S.p.A.

part of the amplification devices. This leads to the generation of harmonic frequencies in the amplified signal, and sub-harmonics in the digitally converted signal after being amplified. The signal filtering after these stages (for example a digital filtering after the acquisition phase or an analog filtering immediately after the saturated amplification stage) can create an output signal with characteristics (amplitude, duration, waveform) similar to a true neuronal action potential, but instead completely artifact due to interference with the noise introduced by the electrical supply network.

This phenomenon can also occur in conditions that are not easily repeatable, such as the switching on and off of equipment connected to the same electrical network as the experimental set-up but not controlled by the experimenter himself, with the possibility of introducing artifact data that are difficult to identify in acquisition phase and consequently difficult to eliminate afterwards.

A fifth limit is the visual interference caused by the cable with automatic subject localization systems. Normally the researcher films the experiment with a camera. The cable can be interposed in the optical line between the camera and the subject, preventing the correct recognition of the subject's silhouette.

A sixth limit is the mechanical fragility of the connection between the electrodes and the cable. Abrupt movements of the subject or experimenter can damage or break this connection.

In the case of small laboratory animals, the damage can also manifest itself as a lesion on the subject which can also lead to serious ones

7462PTIT Notarbartolo & Gervasi S.p.A.

physical consequences such as to compromise both the state of health of the subject and the carrying out of an experiment whose preparation was based on a training period of that specific subject.

To solve these problems, various detection systems have been proposed, including wireless telemetry systems.

In US patent 6,052,619 a portable electroencephalograph is described in which the connection wires between the electrical signal detection system placed on the subject's head and the neurological data acquisition system are replaced with a digital transmitter. In the apparatus described, the electrodes for detecting electrical signals (in the specific case brain waves deriving from the electrical activity of several neurons or neuronal systems) are located on the subject's head and are connected to preamplifiers which are in turn connected to differential amplifiers. whose output is processed by an analog-to-digital converter. The signals are converted from analog to digital in the place where the patient is and are then transmitted by a digital radio transmitter to a receiving unit consisting of a digital radio receiver with a demodulator, an amplifier and filters to separate the demodulated signals into bands. .

The system described provides that this unit is controlled by an expert technician who is able both to select the bands and direct them to a loudspeaker or to a listening headset and to interpret the signal

acoustic output from the speaker, representative of the electrical signals detected by the electrodes.

The advantage of this system lies in having adopted digital technology, both in the signal acquisition phase and in the radio transmission phase.

7462PTIT Notarbartolo & Gervasi S.p.A.

In fact, a desirable condition is to have the signals already in

digital form before transmission to a remote device

reception, as data in digital format are less subject to

errors due to electromagnetic disturbances during the

radio transmission.

However, the application in small laboratory animals still remains

linked to the problem of the size and weight of the devices. Also it

Neuronal and behavioral language study requires

different equipment and methods for measuring potentials

neuronal action, which are weaker and faster signals (and therefore more

difficult to detect) compared to electroencephalographic signals (EEG,

EKG, EMG). The greatest inherent difficulty in measuring the

action potentials compared to other types of neuronal signals implies the

need for greater complexity of the devices that clashes with

difficulty of their integration on a sufficiently small scale

for non-invasive application on laboratory animals.

In US patent 6,654,633 a mobile acquisition system is described

of neurological signals (including neuronal action potentials)

usable on humans or laboratory animals, where these signals are

transmitted analogically, rather than digitally, to a receiving unit

for analysis and in this converted into digital information.

The convenience of this system lies in the compromise of adopting one

analog transmission technology in order to reduce the complexity of the

radio transmitter, and consequently weight and dimensions

of the equipment, with the aim of making it transportable also by a

7462PTIT Notarbartolo & Gervasi S.p.A.

laboratory animal but at the same time renouncing a priori apart

of the advantages, first of all the greater reliability of the received signals

due to a minor degradation of the information content of the

transmitted signals encoded in numerical format, of a technology

purely digital.

It is therefore a first object of the present invention to reduce the weight of the

telemetry system in order to make the device capable of being

smoothly transported not only by human patients but also by

laboratory animals for the purpose of measuring action potentials

neuronal.

It is still an object of the present invention to reduce the size of the

telemetry system by eliminating the presence of the cable in order to increase

the ability to visualize the conditions of the experiment.

It is still an object of the present invention to use

a battery power supply for the telemetry system devices

carried by the subject and applied to it in order to reduce the effects

negatives of ground loops.

It is still an object of the present invention to adopt a detail

technical solution, defined and described in detail below with

name of "operational amplifier configuration from

generalized instrumentation "in the amplification phase inserted in a

signal conditioning chain that includes filtering

analog (digitally controlled) before the conversion phase

analog-digital in order to reduce electrical noise and artifacts in the

7462PTIT Notarbartolo & Gervasi S.p.A.

measurements of neuronal signals deriving from the power supply lines at 50/60 Hz.

Another object of the present invention is to adopt a digital technology also in the signal acquisition and wireless transmission phase in order to increase the reliability of the data received by radio from the subject.

It is a further object of the present invention to adopt an integrated telemetry system in order to eliminate the mechanical connection between the electrodes and the cable, susceptible to breakage and a possible source of injury for the subject.

Another object of the present invention is to provide a software environment for managing the parameters of the transmission device, real-time digital display of the signals and their digital recording compatible with the mathematical analysis software, well known and used by the scientific community, Matlab ( "The MathWorks, Ine., Http://www.mathworks.com") in order to provide an easy methodology for the use of the same invention and the analysis of the data obtained with it.

SUMMARY

The present invention fulfills the aforementioned purposes by providing a neuro-telemetry system which comprises a system of

digital wireless mobile integrated neuronal signal acquisition.

The subject of the invention is therefore an integrated neuro-telemetry system for the acquisition of neuronal electrical signals including:

7462PTIT Λ / ofanbarfo / o & Gervasi S.p.A.

a remote unit (1) for the analog amplification of

neuronal electrical signals detected by one or more electrodes

implanted in selected and connectable brain areas, the

filtering such signals, converting those signals from

analog to digital by means of a microprocessor equipped with

at least one analog / digital converter and transmission

of the same via radio to a receiving station using

an integrated radio transmitter;

a radio base station (2) for receiving packets

of data containing the digital representation of the signals

acquired neuronal electrical signals transmitted to it by the unit

remote (1) and interfaceable with a second

microprocessor for their storage in the

memory of the same, processing and display on

suitable means connectable to it;

a management unit (3) consisting of a computer

connectable to the radio base station (2) and which it controls

both units (1) and (2) by means of a program therein

built-in, establishing a bidirectional connection between the

with a communication protocol suitable for both

management of data packets containing the

digital representation of neuronal electrical signals

acquired and transmitted from the remote unit (1) to the radio station

base (2), and the radio programming of the means of

7462PTIT Notarbartolo & Gervasi S.p.A.

analogue conditioning of the acquired neuronal signal

included in the remote unit (1).

A further object of the invention is a method for the acquisition of

telemetric neuronal electrical signals comprising at least i

steps of:

amplify and condition signals in analog mode

electrodes detected by one or more electrodes implanted in areas

brain choices and produced by neurons;

convert these electrical signals acquired in analog mode

in data packets containing the digital representation of

such neuronal electrical signals;

transmit such data packets containing the

digital representation of these neuronal electrical signals

via radio to a receiving station using a

integrated radio transmitter.

BRIEF DESCRIPTION OF THE DRAWINGS

A detailed description of the system and method will now be provided

for the acquisition of neuronal electrical signals via telemetry of the

present invention, given for illustrative and non-limiting purposes, by doing

reference the attached drawings, in which:

Figure 1 is a schematic representation of the integrated system of

neuro-telemetry of the present invention comprising a unit

remote amplification and analog / digital conversion, filtering, e

radio transmission of neuronal electrical signals, a base station, ed

a management unit;

7462PTIT Notarbartolo & Gervasi S.p.A.

Figure 2 is a schematic representation of the remote unit of the

Figure 1;

Figure 3. is a schematic representation of the radio station of

base of Figure 1;

Figure 4 shows the structural organization of the management unit

of Figure 1;

Figure 5 schematically shows the circuit implementation of the

functions of the remote unit of figure 1;

Figure 6 represents the basic wiring diagram of a stage

to instrumentation amplifier in relation to the changes introduced

on a second "generalized instrumentation amplifier" circuit

the present invention;

Figure 7 represents a replacement bipolar network exemplifying the

operation of the instrumentation amplifier stage

generalized of the previous figure;

Figure 8 represents an exemplary diagram of the gain of

a generalized instrumentation amplifier stage in operation

the frequency of the signal;

Figure 9 visually illustrates the phenomena that

occur in the implementation of the amplifier stage from

generalized instrumentation, according to the present invention;

Figure 10 represents the functional block diagram of the procedure

synchronization, according to the present invention;

Figure 11 represents the functional block diagram of the procedure

acquisition, according to the present invention.

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ì_ 7462PTIT Notarbartolo & Gervasi S.p.A.

Figure 12 represents the functional block diagram of the communication procedure, according to the present invention;

Figure 13 represents the functional block diagram of the configuration procedure, according to the present invention;

Figure 14 represents the time trace of a neuronal signal recorded with an embodiment of the system of the present invention during an exemplary experiment;

Figure 15 is an enlargement of the signal of Figure 14; And

Figure 16 represents a single action potential recorded with an embodiment of the system of the present invention during an example experiment, in relation to the signal to noise ratio.

The present invention allows to overcome the limitations of existing systems and methods by means of an integrated system for acquisition, amplification, analog conditioning, A / D conversion, digital wireless transmission, digital recording and real-time display. of neuronal electrical signals.

Compared to existing systems and to overcome their technical limits, the integrated neuro-telemetry system object of the invention envisages the use of miniaturized components for the electronics relating to the remote unit and an electronic / mechanical design that takes into account the problems previously exposed.

For this purpose, according to the invention a first apparatus is provided as shown in fig. 1 which includes three distinct units connected to each other and these units are: a remote unit (1) connected wirelessly with a second unit consisting of a base station (2) for reception

7462PTIT Notarbartolo & Gervasi S.p.A.

signal and a third system management unit (3) bidirectionally connected to the two previous units (1) and (2) for controlling them.

The remote unit (1), as shown in fig. 2, is an autonomous electronic device which essentially comprises at least:

1. a differential input consisting of two terminals ("input" and "reference") with at least the following electrical characteristics:

input impedance = 10 <10> Ω

input capacitance = 4 pF;

2. a differential amplifier with at least the following electrical characteristics:

common mode rejection = 125 dB

band = DC to 50 kHz

linear gain between 500 Hz and 50 kHz = 3000;

3. a noise reduction device in the 50/60 Hz frequency band which acts by limiting any saturation produced by the noise in the amplification stage;

4. a system of digitally programmable reconfigurable analog filters;

5. an analog-to-digital converter with at least the following

features:

resolution = 8 bits

sampling rate = 20 kHz;

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L 7462PTIT Notarbartolo & Gervasi S.p.A.

6. a microcontroller system comprising at least a RAM, an EEPROM and a CPU;

7. a radio transceiver with digital modulation;

8. an integrated radio antenna;

9. a battery power system for all the parts described above;

In addition, the remote unit (1) with the configuration described above is able to perform the following functions in real time:

a) detection of electrical signals produced by neurons by means of electrodes connected to it;

b) differential amplification of the electrical signals detected with the cancellation of the common mode signals;

c) protection from electrical disturbances in the environment deriving from the 50 / 60Hz power supply lines and relative electromagnetic shielding;

d) analog active filtering of the amplified signal with possibility

digital reconfiguration of the parameters via radio connection with the second unit consisting of the base station (2), by controlling the software incorporated in the management system (3), for the selection of the electrical signals of interest;

e) analog to digital conversion of the filtered electrical signals;

f) encoding of neuronal data in packets, addition of numbers

sequential and system status "flags";

g) management of digital controls and digital radio communication protocols with the base station (2) by means of a system a

7462PTIT Notarbartolo & Gervasi S.p.A.

microprocessor equipped with calculation capabilities and software capable of guaranteeing that the execution of all the instructions takes place at most with a finite time delay ("real-time" system);

h) modulation of the transmitted data and demodulation of the received data by means of an integrated radio transceiver with modulation speed sufficient to establish a bidirectional connection between the remote unit (1) and the base station (2) without violating the "real-time" condition "described in the previous point;

i) electrical isolation of the neuronal telemetry system to limit the problems deriving from ground loops;

j) integration including the reduction of the weight and dimensions of the devices in order to meet the requirements of mechanical stability and physical tolerability of the telemetry system by the subject and the invasiveness limitations of the telemetry system with respect to its use in combination with systems image shooting;

k) monitoring of the state of charge of the battery.

The radio base station (2) shown in Figure 3 is an electronic device which essentially comprises at least:

1. a radio antenna;

2. a radio transceiver with digital modulation;

3. a microcontroller system comprising at least a RAM, an EEPROM and a CPU; and

4. an interface for data exchange between the microcontroller system and a personal computer.

7462PTIT Notarbartolo & Gervasi S.p.A.

According to this configuration, the radio base station (2) is able to perform the following functions in real time:

a) mutual coupling of a pair of devices - remote unit (1) and base station (2) - with dynamic self-assignment of identification addresses of the pair and of the radio channel even in the presence of other devices that transmit on the same radio frequency bands ;

b) mutual synchronization of the internal clocks of the engaged couple;

c) hang up during temporary loss of the radio signal and interference with other devices and dynamic reassignment of the identification addresses;

d) reception of the packets containing the data encoding the neuronal signals acquired and transmitted by the remote unit (1);

e) checking the integrity of the data packets received and generating error codes for identifying erroneous packets;

f) transmission of the configuration parameters of the programmable analog filters to the remote unit (1);

g) transmission of the management parameters to the remote unit (1) from the management software (3);

h) transmission of the settings to the remote unit <1> (1) concerning the

how to select the acquired neuronal signals to be transmitted to the base station (2);

i) receipt of data relating to the state of charge of the battery and status variables of the remote unit (1);

7462PTIT Notarbartolo & Gervasi S.p.A.

j) management of the communication protocol with the software

management (3) residing in a personal computer.

With reference to fig. 4, the management unit (3) is a computer

interfaced with the radio base station (2) and that for the management of the

remote unit (1) and the same base station (2) and for processing

of the data corresponding to the neuronal signals incorporates a software of

control that performs at least the following functions of:

a) management of data exchange with the base station (2);

b) management of the parameters of the remote unit (1);

c) management of the base station (2);

d) real-time digital display of the data they represent

neuronal signals;

e) real-time storage in digital format of the data that

represent neuronal signals;

f) user interface for the management of programmable analog filters

remote unit (1).

The electronic circuit of the remote unit (1) is described below in

refer to figure 5. Differential amplifiers A2e d Αήcon factor

open loop amplification K capture the neuronal signal

in the form of electrical potential difference applied between the inputs in

and ref (respectively "input" and "reference") and produce the signals of

output A <+> and A <'> which are respectively the difference between the signal in and

the feedback β <+> and the difference between the signal ref and the feedback β <'>,

both multiplied by the amplification constant K. The signals β <+> and β <">

they are generated starting from A <+> and Α <'>. The differentiator Δ reproduces between

7462PTIT Notarbartolo & Gervasi S.p.A.

Δ <+> and A the same potential difference between the signals A <+> and A The conditioner β receives in input the difference between Δ <+> and A and multiplies it in the frequency domain by its transfer function H ( s). The result is the potential difference between the feedbacks fi and p. The closure of this loop feedback establishes instant by instant the value of the difference between Δ <+> and A which the differentiator evaluates by generating the output signal Δ <0>, which is transmitted as an input to the filter F. All behavior is 'described mathematically by the following equations:

A <+> - A <~> = K (in - fi) - K (ref-fi) = K (in - ref) - K (fi - fi)

1. <A <+> - A <~> = Δ <+> - Δ <~>

F -p- = H (s) - (- A)

2. A ° = lim

K → + ∞

The purpose of this circuit configuration, which we call "generalized instrumentation amplifier", is precisely to arrive at its function described by equation 2 and is guaranteed by the choice of differential amplifiers with high open-loop amplification factor K.

In fact, an appropriate choice of the transfer function H (s) of the conditioning circuit /? it allows the filtering of frequency components around 50 / 60Hz, which have a voltage level higher than the signal

neuronaie, avoiding saturation of the amplification stage.

In light of this formulation in a normal amplifier stage in an "instrumentation amplifier" configuration (see figure 6), described in the electronic circuit literature, the function of

7462PTIT Notarbartolo & Gervasi S.p.A.

transfer H (s) calculated between the quadripole β, which has as inputs i

nodes Δ <*> and Δ and as the nodes / Γ and β come out, it is worth: ;; ;; this corresponds to a gain of the output signal Δ <0> with respect to the differential input signal in-ref equal to: ;; 4. G = '<~ R> ° <+ 2R>; H (s) R G, ;; that is therefore to the value of the gain of an amplifier stage in an "instrumentation amplifier" configuration, as known from the electronic literature. ; The advantage of the analytical formulation proposed here (equations 1. and 2.); lies in the fact that through it it is evident that in the instrumentation amplifier configuration the gain G, as reported; in equation 4., it is only a particular case of a circuit configuration, which we therefore call "generalized instrumentation amplifier", in which the choice of the function H (s) of the quadripole; which has the nodes Δ <+> and Δ as inputs and the nodes e p and has been restricted to a constant value G in the frequency domain. In an application of the generalized instrumentation amplifier configuration, replacing the resistor RQ with a; bipole illustrated in figure 7, of impedance: ;; ; 7462PTIT Notarbartolo & Gervasi S.p.A. ;; and substituting this expression for RG in equation 4. we obtain the transfer function GfsJ between the differential input in-ref ;; ;;; which is of the general form: ;; ;;; From equation 7. it can be seen that the asymptotic trend of the gain as a function of frequency is divided into two regions having limit values: ;; lim; <s → 0>; 8. i; lim; s → + ∞ ;; whose modulus course can be seen in Figure 8.; The asymptotic values of the transfer function for the limiting cases of the signal frequency tending to zero or infinity can be calibrated with a choice of values for the network components in Figure 7 so that the qualitative curve in figure 8, whose meaning is the modulus of the frequency response of the amplifier gain, has a low value; for frequencies lower than 50/60 Hz and higher for higher frequencies. ; A spectral analysis of the frequency content of action potential signals, such as stereotypic waveform signals, shows; 7462PTIT Notarbartolo & Gervasi S.p.A. that they contain no significant frequency components below frequencies of the order of 1kHz, corresponding to the reciprocal of the typical duration of an action potential of 1ms. ; A further analysis of the H (s) function, reciprocal of the G (s) function; designed in the implementation of the instrumentation amplifier; generalized described, shows that the role of the β quadrupole is to; leave the components of low frequency (noise at 50/60 Hz); and to attenuate signals having high frequency components (signal; neuronaie). ; The amplification of the neuronal signal is due to the fact that the aforementioned; quadripole is inserted in a feedback loop consisting of the amplifiers; differentials of the generalized amplifier configuration which, due to the circuit network they describe, operate the reciprocal of the ; transfer function H (s) in the frequency domain. In this way, what the quadripole β attenuates at its exit between the nodes β * and β,

it is amplified in the signal present at nodes Δ <+> and A, reported by the

differentiator Δ from amplifiers Ai and A2, and which turns out to be allo

at the same time the input for the β quadripole and the differential signal of

Δ <0> output of the generalized instrumentation amplifier.

This application example illustrates an inherent advantage of the

generalized configuration in relation to the saturation problem

of the input amplifier stages.

Figure 9 shows an example of the operating cycle of the functions

internal amplification of a neuronal signal, represented by

small fluctuations, superimposed on a large noise component a

7462PTIT Notarbartolo & Gervasi S.p.A.

50Hz for a generalized instrumentation amplifier stage calculated for a gain of 1000 on the neuronal signal band.

Note how in this case the amplification of neuronal action potentials is independent of the conditioning of the component of

noise at 50Hz, presenting a relative gain of 1000 times provided that the signal component at 50Hz is not amplified and

that in any node of the stage it does not have a voltage higher than

the one present at the entrance.

In this example, therefore, an action potential of 1mV can be amplified 1000 times up to the value of 1V, without a component of

superimposed noise with an amplitude of 1V is amplified by the same

factor 1000 thus avoiding the saturation of the input stage which otherwise would have compromised the amplification of the action potential.

Subsequently the pre-amplified and conditioned signal is filtered

in frequency from block F, which receives the parameters for filtering from

CPU block.

The programmable filter F operates two functions: the first is the elimination of the residual noise at 50 / 60Hz, the second consists in filtering the neuronal signal within its band in a way that can be controlled by the operator by setting the parameters through the software

management (3).

The choice of the amplifier configuration from generalized instrumentation operating a pre-filtering combined with the final filtering of the programmable filter F constitutes a solution to the problem of reduction

7462PTIT Notarbartolo & Gervasi S.p.A.

of the noise and saturation of the amplifiers which, in the light of the

formulation and the proposed analysis are two problems

interdependent due to the non-commutability of the operations

amplification-differentiation-filtering in an amplification regime

non linear in case of saturation.

The non-commutability of the operations is not evident in the case of

a linear theory of circuits within which the configuration

standard of instrumentation amplifiers, described in the literature

electronics, originated.

The filtered signal is converted from analog to digital by the ADC block

which communicates with the MCU block for data acquisition in

digital. The MCU block also manages the data exchange with the block

RTX, which creates the radio link with the base station (2) for

the sending of the acquired neuronal data and the dialogue for the setting of the

controls that takes place through the management system software (3).

The remote unit (1) implements its functions both through the hardware

previously described, both through resident software procedures

in the MCU block. The synchronization procedure, described in the “flow

chart "in figure 10, is performed first when the unit is turned on

remote (1). It is also performed every other time it is required for

reasons for synchronization loss.

The synchronization procedure implements the radio link between

the remote unit (1) and the radio base station (2), receiving the parameters

of the connection, those for the ADC analog-to-digital converter and for the

programmable filter F. If synchronization is lost all

7462PTIT Notarbartolo & Gervasi S.p.A.

parameters are re-initialized and the sequence is repeated until yes

achieves a stable connection condition. Hence the converter

analog-digital ADC and filter F are programmed. Established the

synchronization the remote unit (1) carries out the data acquisition

generated by the analogue-digital conversion of the neuronal signal

amplified, according to the flow diagram shown in fig. 11.

The acquisition procedure signals the CPU to start the conversion

analog-to-digital and full conversion to be able to process data

for transmission to the radio base station (2).

The data prepared for transmission is copied into the register of

TX Buffer memory, the time necessary for the

reacquisition, then the whole procedure is repeated in cycle.

The communication procedure manages the radio communication between

the remote unit (1) and the base station (2) according to the diagram of

flow shown in fig. 12.

This procedure transmits data from the remote unit (1) to the

management system (3). The communication procedure reads

continuously the TX Buffer memory register, constantly filled

from the acquisition procedure. If it is full it turns on the

radio transmitter, loads the data to be transmitted into the transmitter, there

transmits and turns off the transmitter. After these operations check if

the remote unit (1) needs to receive data from the management system

(3). If not, continue to check the TX Buffer, otherwise yes

takes care of turning on the radio receiver to receive any data

by the management system (3). If there is no data, the

27 Pi 7462PTIT Notarbartolo & Gervasi S.p.A.

receiver and the procedure is repeated as previously described. In

case of data received from the management system (3), the remote unit (1) activates the

configuration procedure.

The configuration procedure manages the data received from the system

management (3) on the remote unit (1) for the management of settable parameters

by the user and the data relating to the communication protocols coming into

autonomous mode from the radio base station (2) according to the diagram of

flow shown in figure 13.

The description of an example of embodiment of the

system of the present invention.

Example of an integrated neuro-telemetry system

Characteristics of the remote unit (1):

- electronics: SMD components (Surface Mounted Devices) mounted on a

PCB (Printed Circuit Board) multilayer with internal ground planes ed

external for electromagnetic shielding, battery powered

rechargeable lithium polymer, LED (Light Emitting Diodes) of

signaling for variables and status flags, microcontroller system,

radio section (including integrated antenna) operating in the

2.4GHz frequencies, multifunction button for reset and local settings,

FPAA (Field Programmable Analog Array) for analog filtering

digitally programmable, service USB (Universal Serial Bus) port

for local unit software updates, differential amplifiers

implementing the "instrumentation amplifier" solution

generalized "previously described.

28

Ae7462PTIT Notarbartolo & Gervasi S.p.A.

- mechanics: casing with conductive metallic coating for the

protection of the system from electromagnetic disturbances, electrode in

tungsten encapsulated in a silicon microtube inserted into a guide a

coaxial sliding consisting of a connected steel microtube

mechanically and electrically to the metal container for

the implementation of mechanical support and shielding

electrode electromagnetic, mechanical translation system

miniaturized for the linear sliding advancement of the electrode

inside the coaxial guide with integrated micrometric adjustment

on the PCB and electromagnetically shielded by the enclosure a

metallic coating.

Base station features (2):

- electronics: SMD components (Surface Mounted Devices) mounted on a

PCB (Printed Circuit Board) multilayer with internal ground planes ed

external for electromagnetic shielding, USB port (Universal Serial

Service bus) for local software updates of the unit and for the

communication with a PC on which the management software is installed

(3), power supply via USB port, microcontroller system,

radio section (including integrated antenna) operating in the

frequencies at 2.4GHz.

Management software features (3):

- interfacing: management of the USB connection between software (3) and

hardware (2)

- protocols: decoding of packets received by the base station (2) e

dialogue with it through a USB port

7462PTIT Notarbartolo & Gervasi S.p.A.

- management: real-time display of data in the form of a trace

digital oscilloscope on the PC monitor connected to the base station

(2), graphic interface with icons and buttons for control

acquisition, saving on hard disk of the data in phase

acquisition (all included in the Matlab software environment - "The

MathWorks, Ine., Http: //www.mathworks.corn '<1>).

With a system just described, a method is implemented for

the acquisition of neuronal electrical signals via telemetry

including at least the steps of:

amplify and condition signals in analog mode

electrodes detected by one or more electrodes implanted in areas

brain choices and produced by single neurons;

convert these electrical signals acquired in analog mode

in data packets containing the digital representation of

such neuronal electrical signals;

transmit such data packets containing the

digital representation of these neuronal electrical signals

via radio to a receiving station using a

integrated radio transmitter;

receive such data packets containing the representation

digital neuronal electrical signals in a station

receiving and verifying the integrity of the information content,

generating any error signals for the management of the

communication protocol between transmitter and receiver;

7462PTIT Notarbartolo & Gervasi S.p.A.

interface the receiving station with a computer in

able to read the digital neuronal data received from the

station and to communicate telemetry data with it

service, such as setting parameters for filters

in the remote transmission unit and system flag;

view the neuronal data received in real time

as an oscilloscope trace in a window

user-visible software;

check the operating modes of the remote transmitter

working from the computer connected to the base station

taking advantage of the bidirectionality of the wireless connection between

remote transmitter and receiving station;

store in digital format the data received from the station

receiver in the computer connected to it;

manage remote transmitter control operations,

monitor the view and save data from it

received by acting through the Matlab software environment ("The

MathWorks, Ine., Http://www.mathworks.com "):

A typical experiment for acquisition, amplification, the

analog conditioning, A / D conversion, wireless transmission

digital, digital recording and real-time viewing of

neuronal electrical signals performed according to the above method

and with the integrated system of the invention is described below.

31

<■> IS 7462PTIT Notarbartolo & Gervasi S.p.A.

The following protocol for recording neuronal action potentials is in accordance with NIH institutional and international standards for the treatment and use of animals for scientific research purposes.

This protocol is compatible with the procedures for recording neuronal signals that use equipment already existing on the market, making it possible to compare the results.

Neuro-telemetry example

Subject

• adult male Wistar rat, weight 250-300g.

Materials

• anesthetic: urethane, dose 1.5g / kg [urethane weight / subject weight], concentration 30% [urethane weight / H2O weight].

• electrodes: single tungsten (Frederick Haer & Co., 9 Main

St., Bowdoinham, ME 04008 USA), impedance = 1.0 - 1.2 Megaohm

• wooden stick with cotton end

Instrumentation

• table with stereotaxic supports

• thermostated heating plate

Preparation of the subject

The subject is anesthetized with intraperitoneal injection of urethane, dose 1.5g / kg [urethane weight / subject weight], concentration 30% [weight

urethane / weight H2O]. After the induction of anesthesia, the subject is placed on the heated plate thermostated at a temperature of 37.5 ° C.

7462PTIT Notarbartolo & Gervasi S.p.A.

The subject is kept stationary for the entire duration

of the experiment by monitoring the retraction of the hind legs to one

light compression with tweezers, corneal reflexes and rhythm

respiratory as indices of the state of anesthesia. In case of necessity

An extra dose of anesthetic equal to 10% of the dose is given

initial.

After fixing the subject's head to the stereotaxic support, the

left somato-sensory cerebral cortex is exposed by

a 3x3mm opening craniotomy, centered at the coordinate point

2mm rear and 6mm lateral to bregma (reference point

craniometric, frontal intersection of the cranial sutures).

The region corresponding to the neuronal representation of the vibrissae

("barrei cortex") is identified according to the configuration

cerebral vascular and stereotaxic coordinates.

Neuronaie registration

A single connected electrode is mounted on the remote unit (1) e

conducted in the affected region (barrei cortex) by penetrating the tissue

cerebral to a depth of 700-1000 microns.

The gain of the amplifier is set to the value of 5000 and the filter

is set as a Butterworth band pass of the 4th <Λ> order with

lower cut-off frequency of 250Hz and higher than 7500Hz. There

signal digitization is set with a frequency of

20kHz sampling and 8bit resolution.

The receiving unit (2) is placed away from the remote unit (1) within a

radius that can arbitrarily vary up to 5 meters in an environment in

7462PTIT Notarbartolo & Gervasi S.p.A.

presence of other electronic equipment (for example a

laboratory for electrophysiological recordings) and is connected to a

laptop through a Universal Serial Bus (USB) port. In

these conditions the integrity index of the wireless radio link,

defined as the ratio of correctly transmitted data packets e

received between remote unit (1) and base station (2) and data packets

received with radio interference signaling flags, it appears to be del

98.3%. Consequently the packet selection protocol

distinguishes 100% reliable digital neural data by identifying packets

of data classified as "correct" from "incorrect" allowing the

management software (3) to view and archive a continuous trace

of reliable neuronal data and simultaneously a binary trace

containing the state of the radio interference signaling flag, so on

provide the operator with both a graphical display of the data in real time

amplified neuronal signals, both a visual indication of the flag of

radio interference. The graphical trace of the correct packages also comes

converted into an audio signal synchronized with the same: by monitoring

the video trace of the neuronal signals and the audio signal the operator can

act on the electrode positioning system using both

representations of neuronal signals as a control of the depth of

penetration into the brain tissue in order to optimize the quality of the

acquired signal.

The absence of the ground loop between the amplification system in the remote unit

(1) and computer connected to the base station (2) allows feasibility

of the experiment even with the subject isolated from the ground potential

7462PTIT Notarbartolo & Gervasi S.p.A.

and outside other systems for electromagnetic shielding

(e.g. Faraday cages).

Tactile stimulation

A tactile stimulus, contralateral (opposite side) to the craniotomy e

consisting of a mechanical vibration, is applied to the vibrissae

using the cotton swab.

Measurements analysis

Neuronal activity is characterized by the presence of action potentials

neuronal. Under the experimental conditions described a system of

neuronal recording must be able to detect potentials

action in the face of a tactile stimulus contralateral to the region in which it is

find the electrode (region of the craniotomy).

The condition for checking that the recorded signal is actually

correlated to the tactile stimulus is the absence of neuronal response when it is

same tactile stimulus is ipsilateral (same side) instead of contralateral

(opposite side). The presence of a latency of 7-10 ms between the instant of

tactile stimulation and neuronal activity indicates that the activity is like

physiological response to the stimulus.

Figure 14 illustrates some typical signals recorded in the

experimental conditions described above. The trace represents a

10 second sample of neuronal signal recorded by the system

while tactile stimulation was in progress.

There are three groups of neuronal impulses (left) followed by five others

groups (right) in correspondence of three and then five

stimulations of a vibrissa, whose neuronal path starts from the cells

7462PTIT Notarbartolo & Gervasi S.p.A.

mechano-receptors around the follicle and along which tactile information travels to the corresponding barrei in the somatosensory cortex where the electrode has been placed, via the cotton swab. In the intermediate time intervals to the groups of neuronal impulses, the absence of neuronal activity is noted, as well as a low level of electrical fluctuations.

The stereotypical form of the action potential is easily recognized by a reading of the same signal displayed on a smaller time scale. The trace in figure 15 is an enlargement of the signal fragment corresponding to a time span of 20 msec. which includes the fourth group of impulses (the first of the second series of five groups on the right) contained in the previous track.

A sequence of seven neuronal action potentials recorded in response to a single tactile stimulation is identified. A single action potential is instead shown in the trace in figure 16.

The action potential appears in the center of the figure. Note how the small fluctuations of the trace before and after the action potential, corresponding to the sum of other signals which are not of interest for neuronal coding and which can consequently be defined as noise, remain centered and limited to a value of amplitude

significantly lower than the action potential, which remains visibly recognizable.

Validation of the measure

The verification of the waveform of the action potential, together with the verification of the responses to the stimulus in the experimental condition and in the

7462PTIT Notarbartolo & Gervasi S.p.A.

control condition, constitutes the validating proof of the correctness

functioning of the neuronal recording system of the present

invention and according to what is illustrated and described.

Claims (8)

• W fc w w u n u U U J H o 7462PTIT Notarbartolo & Gervasi S.p.A. CLAIMS 1. Mobile system for the acquisition of neuronal action potentials and their digital telemetry transmission in real time wireless comprising: to. a remote unit (1) for the analog amplification of neuronal electrical signals detected by one or more electrodes implanted in brain areas selected and connected to it, the filtering of these signals, the conversion of these signals from analog to digital by means of a microprocessor equipped with at least one analog / digital converter and the transmission of the same via radio to a receiving station by means of a radio transmitter integrated; b. a radio base station (2) for receiving packets of data containing the digital representation of the acquired neuronal electrical signals transmitted to it by the remote unit (1) and interfaced with a second microprocessor for their storage in its memory, processing and display on suitable means that can be connected to it; And c. a management unit (3) consisting of a connectable computer to the radio base station (2) and which controls both units (1) and (2) by means of a program incorporated therein, establishing a bidirectional connection between them with a communication protocol suitable for both the management of data packets containing the digital representation of the neuronal electrical signals acquired and transmitted by the remote unit (1) to the radio base station (2), both to programming via 7462PTIT Notarbartolo & Gervasi S.p.A. radio of the analog conditioning means of the acquired neuronal signal included in the remote unit (1). 2. Mobile system for the acquisition of neuronal action potentials according to the previous claim, wherein said remote unit essentially comprises at least: to. a differential input consisting of two terminals ("input" and "reference") with at least the following electrical characteristics: input impedance = 10 <10> Ω input capacitance = 4 pF; b. a differential amplifier with at least the following electrical characteristics: common mode rejection = 125 dB band = DC to 50 kHz linear gain between 500 Hz and 50 kHz = 3000; c. a noise reduction device in the frequency band 50/60 Hz which acts by limiting any saturation produced by the noise in the amplification stage; d. a system of digitally programmable reconfigurable analog filters; And. an analog-to-digital converter with at least the following characteristics: resolution = 8 bits sampling rate = 20 kHz; f. a microcontroller system comprising at least one RAM, an EEPROM and a CPU; 7462PTIT Notarbartolo & Gervasi S.p.A. g. a radio transceiver with digital modulation; h. an integrated radio antenna; and the. a battery power system for all parts previously described. 3. Mobile system for the acquisition of neuronal action potentials according to claim 1 or 2, wherein said radio base station essentially includes at least: to. a radio antenna; b. a radio transceiver with digital modulation; c. a microcontroller system comprising at least one RAM, an EEPROM and a CPU; And d. an interface for exchanging data between the system a microcontroller and a personal computer. 4. Method for acquiring neuronal electrical signals by way telemetry, characterized by the fact of understanding at least the steps from: to. amplify and condition electrical signals in analog mode detected by one or more electrodes implanted in selected brain areas e produced by neurons; b. convert these electrical signals acquired in analog mode into data packets containing the digital representation of such neuronal electrical signals; c. transmit such data packets containing the representation of these neuronal electrical signals via radio to a station reception by means of an integrated radio transmitter; 7462PTIT Notarbartolo & Gervasi S.p.A. d. reduce the weight of the telemetry system in order to make the device capable of being transported in a non-easy way only from human patients but also from laboratory animals al end of measurement of neuronal action potentials; And. use battery power for system devices telemetry carried by the subject and applied to it for the purpose to reduce the negative effects of ground loops \ f. adopt an operational amplifier configuration from generalized instrumentation during the inserted amplification phase in a signal conditioning chain that provides for an analog filtering (digitally controlled) before the analog-digital conversion phase in such a way as to reduce electrical disturbances and artifacts in the measurements of neuronal signals deriving from the 50/60 power supply lines Hz; g. adopt digital technology even in the acquisition phase signal and wireless transmission; h. adopt an integrated telemetry system to eliminate the mechanical connection between the electrodes and the cable; And the. provide transmission device parameter management software environment, digital display in time of the signals and their digital recording which is compatible with a mathematical analysis software. 5. Method for the acquisition of neuronal electrical signals by telemetry according to the previous claim, in which the management of an autonomous electronic device is provided 7462PTIT Notarbartolo & Gervasi S.p.A. remote or remote unit, called management by providing for it to be carried out in real time of the following functions: to. detection of electrical signals produced by neurons by means of electrodes connected to it; b. differential amplification of the electrical signals detected with the cancellation of the common mode signals; c. protection from electrical disturbances in the environment resulting from the 50 / 60Hz power supply lines and relative electromagnetic shielding; d. active analog filtering of the amplified signal with the possibility of digital reconfiguration of the parameters via radio connection with the second unit consisting of the base station (2), by means of the control of the software incorporated in the management system (3), for the selection of electrical signals interest; And. analog to digital conversion of filtered electrical signals; f. encoding of neuronal data in packets, addition of sequential numbers and system status "flags"; g. management of digital controls and communication protocols digital radio with the base station (2) using a system with microprocessor equipped with calculation and software capabilities in able to ensure that the execution of all instructions occurs at most with a finite time delay (system "real-time") ·, 7462PTIT Notarbartolo & Gervasi S.p.A. h. modulation of the transmitted data and demodulation of the received data by integrated radio transceiver with speed modulation sufficient to establish a bidirectional connection between the remote unit (1) and the base station (2) without violating the "real-time" condition described in the previous point; the. electrical isolation of the neuronal telemetry system to limit the problems deriving from ground loops \ j. integration including the reduction of the weight and dimensions of the devices in such a way as to satisfy the requirements of mechanical stability and physical tolerability of the system telemetry by the subject and the limitations of invasiveness the telemetry system; And k. battery charge status monitoring. 6. Method for the acquisition of neuronal electrical signals by telemetry according to claim 4 or 5, in which the management of an electronic device such as a radio station of basis, the management method by foreseeing the execution on time at least of the following functions: to. mutual coupling of a pair of devices - remote unit (1) and base station (2) - with dynamic self-assignment of identification addresses of the pair and of the radio channel even in presence of other devices that transmit on them radio frequency bands; 7462PTIT Notarbartolo & Gervasi S.p.A. b. mutual synchronization of the internal clocks of the engaged couple; c. hang up during temporary loss of the radio signal and interference with other devices and dynamic reassignment of the identification addresses; d. reception of packets containing the data encoding the neuronal signals acquired and transmitted by the remote unit (1); And. checking the integrity of the data packets received and generating error codes to identify incorrect packets; f. transmission of the configuration parameters of the programmable analog filters to the remote unit (1); g. transmission of the management parameters to the remote unit (1) from the management software (3); h. transmission of the settings to the remote unit (1) regarding the selection modalities of the acquired neuronal signals to be transmitted to the base station (2); the. reception of data relating to the state of charge of the battery and status variables of the remote unit (1); j. management of the communication protocol with the management software (3) residing in a personal computer. 7. Software for the system and method of the preceding claims, characterized in that it implements at least the functions of: to. management of data exchange with the base station (2); b. management of the parameters of the remote unit (1); 7462PTIT Notarbartolo & Gervasi S.p.A. c. base station management (2); d. real-time digital visualization of data representing neuronal signals; And. real-time digital storage of data representing neuronal signals; f. user interface for the management of the programmable analog filters of the remote unit (1); g. the synchronization procedure described in the flow chart in figure 10; h. the acquisition procedure described by the flow chart in the figure 11; the. the communication procedure described by the flow chart in the figure 12; And j. the configuration procedure described by the flow chart in the figure 13. 8. Circuit configuration for the software, system and method of the preceding claims, characterized in that it comprises: to. the wiring diagram shown in figure 6; b. the replacement bipolar network shown in Figure 7; c. the gain diagram shown in Figure 8; d. the visual explanation of the operation of the stage shown in Figure 9; And And. equations 1 to 8. (IAC / EM / pd) Padua, 21 September 2006 7462PTIT Notarbartolo & Gervasi S.p.A. p. International Higher School of Advanced Studies The agent Notarbartolo & Gervasi Spa